The bearing capacity of building fasteners needs to be comprehensively judged based on the type, material, installation specifications, and stress form. Its core indicators are reflected in the performance of anti sliding, anti damage, anti torsion, etc., as follows:
From the perspective of standard requirements, according to the "Steel Pipe Scaffold Fasteners" (GB 15831), the bearing capacity of qualified fasteners must meet the following requirements: the anti sliding bearing capacity design value of right angle fasteners and rotating fasteners is 8kN (i.e. the maximum force that does not cause relative sliding between the steel pipe and the fastener under load); Anti destructive bearing capacity ≥ 25kN (minimum load at which the fastener fails); The design value of the shear bearing capacity of the docking fastener is 3kN, and the anti failure bearing capacity is ≥ 10kN. The tightening torque of the bolt should be controlled at 40-65N · m, which can ensure that the clamping force of the fastener on the steel pipe reaches 2.5-3.5kN, which is the basis of the bearing capacity.
In practical applications, the bearing capacity is affected by various factors: in terms of material, the bearing capacity of malleable cast iron (KT33-8) fasteners is better than that of inferior gray cast iron, which may fracture below 10kN; During installation, if the bolts are not tightened to the specified torque (such as only 20N · m), the anti slip bearing capacity will decrease to below 5kN; The wear and corrosion of threads caused by repeated use can also reduce the load-bearing capacity by more than 30%.
In different stress scenarios, the load-bearing capacity of fasteners needs to match the load: when the vertical load transmitted by the scaffold pole is transmitted through right angle fasteners, the single fastener needs to be controlled within 8kN (approximately equivalent to 2-3 layers of scaffold boards and construction loads); The horizontal force of the horizontal bar is borne by the rotating fastener and should be ≤ 8kN; when the docking fastener is used for steel pipe extension, the shear bearing capacity of 3kN should be matched with the axial force of the steel pipe.
In summary, the design bearing capacity of qualified building fasteners is: anti slip 8kN, anti damage ≥ 25kN (right angle/rotary fasteners), and anti shear 3kN (butt fasteners). In actual use, it is necessary to ensure its performance meets the standards through standardized installation and maintenance.
